feat: industry-grade SEO audit engine + plan flow fix (v1.7.0)

CHANGELOG.md

@@ -5,6 +5,37 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [1.7.0] - 2026-03-18 20:44 UTC
+
+### Added
+- **Comprehensive SEO Audit Engine** — Industry-grade URL analysis modeled after Screaming Frog, Ahrefs, Sitebulb, and Semrush
+  - Full meta tag analysis: title (length/status), description (length/status), keywords, viewport, charset, robots directives
+  - Open Graph & Twitter Card validation
+  - Heading structure audit: H1 count check, hierarchy analysis (H1-H6), multiple H1 detection
+  - Link analysis: internal/external/nofollow counts, external link sampling
+  - Image audit: total count, alt text coverage %, lazy loading detection, missing alt samples
+  - Content analysis: word count, sentence count, paragraph count, avg words/sentence
+  - Structured data detection: JSON-LD, Microdata, 12+ schema types (Article, FAQ, Product, LocalBusiness, etc.)
+  - Performance signals: server info, response time, HTML size, external scripts/stylesheets, inline styles, preconnect/preload/dns-prefetch, async/defer detection
+  - Accessibility checks: lang attribute, ARIA labels, first image alt text
+  - Hreflang tag detection for international SEO
+  - Canonical tag validation with mismatch detection
+  - **Automated scoring**: Overall, Technical, Content, Performance, Social scores (0-100)
+  - **Issue detection**: Critical/Warning/Info severity levels across all categories
+- **Plan-First Flow Fix** — Non-code agents (SEO, content, SMM, design, web, app) now bypass the plan-first workflow
+  - No more "Start Coding" or "Modify Plan" buttons for non-code agent responses
+  - SEO agent goes straight to preview mode after generating audit reports
+  - Plan card only shown for code/general agents
+
+### Changed
+- `/api/fetch-url` route completely rewritten: 300+ lines of comprehensive HTML parsing and scoring
+- SEO agent data injection now passes structured audit data with scores, issues, and category breakdowns
+
+### Technical Details
+- Files modified: 5 (AIAssist.tsx, qwen-oauth.ts, ollama-cloud.ts, zai-plan.ts, openrouter.ts)
+- Files rewritten: 1 (`app/api/fetch-url/route.ts` — complete rewrite)
+- New component-level guard: `isCodeAgent` condition for plan-first workflow
+
 ## [1.6.0] - 2026-03-18 20:34 UTC
 
 ### Added